show your colours

show (one's) (true) colours

To reveal what one really believes, thinks, or wants; to act in accordance with one's real personality, character, or disposition. Primarily heard in UK. Dave said all along that he only wanted this deal because it was in the company's best interest, but he showed his true colours once he realised that he wouldn't get any special commission for his efforts. It's only in times of crisis that your friends will really show their colours.
See also: colour, show

show your (true) colours

reveal your real character or intentions, especially when these are disreputable or dishonourable.
See also: colour, show
References in periodicals archive ?
It supports grassroots sports and education across the region, and annually uses the derby match - the latest taking place on October 27 - to run its Show Your Colours campaign, encouraging businesses, schools and community groups to not only wear the colours of their favourite team but to also buy Show Your Colours raffle tickets.
Foundation of Light spokesman Phil King said: "I must express our gratitude to Newcastle United for supporting this campaign by providing a signed shirt for the Show Your Colours raffle.
And you can show your colours with our ECHO commemorative banners printed especially for the Merseyside derby.
So whether you're a Liverpool or an Everton fan make sure you get your free banner with the ECHO and show your colours.